Light emitting device

Abstract

A light emitting device has a covering member. The covering member includes light reflecting material and a second fluorescent material, and a dominant wavelength of an emission spectrum of the second fluorescent material differs from a dominant wavelength of an emission spectrum of the light emitting device by 30 nm or less. The light emitting device emits light with chromaticity that is within a four-sided region on a CIE 1931 chromaticity diagram, where chromaticity coordinates (x, y) are (0.645, 0.335) at a first point, (0.665, 0.335) at a second point, (0.735, 0.265) at a third point, (0.721, 0.259) at a fourth point, and a first line joins the first and second points, a second line joins the second and third points, a third line joins the third and fourth points, and a fourth line joins the fourth and first points to define the four-sided region of the chromaticity diagram.

What is claimed is: 
     
       1. A light emitting device comprising:
 a light emitting element having a dominant wavelength in a range greater than or equal to 380 nm and less than or equal to 470 nm; 
 a wavelength conversion member that is disposed on the light emitting element and comprises a first fluorescent material; and 
 a covering member that covers the sides of the wavelength conversion member and surrounds the light emitting element, 
 wherein the light emitting device has an emission spectrum having a dominant wavelength in a range greater than or equal to 610 nm and less than or equal to 780 nm, 
 wherein the covering member comprises light reflecting material and a second fluorescent material, 
 wherein a dominant wavelength of an emission spectrum of the second fluorescent material differs from the dominant wavelength of the emission spectrum of the light emitting device by less than or equal to 30 nm, and 
 wherein a chromaticity of light emitted by the light emitting device is within a four-sided region on a CIE 1931 chromaticity diagram, where chromaticity coordinates (x, y) are (0.645, 0.335) at a first point, (0.665, 0.335) at a second point, (0.735, 0.265) at a third point, (0.721, 0.259) at a fourth point, and a first line joins the first and second points, a second line joins the second and third points, a third line joins the third and fourth points, and a fourth line joins the fourth and first points to define the four-sided region of the chromaticity diagram. 
 
     
     
       2. The light emitting device as cited in  claim 1  wherein the second fluorescent material of the covering member comprises at least one compound selected from (Ca, Sr)AlSiN 3 :Eu and (Ca, Sr, Ba) 2 Si 5 N 8 :Eu. 
     
     
       3. The light emitting device as cited in  claim 1  wherein the first fluorescent material of the wavelength conversion member comprises at least one compound selected from (Y, Gd, Tb, Lu) 3 (Al, Ga) 5 O 12 :Ce, (Ca, Sr)AlSiN 3 :Eu, and (Ca, Sr, Ba) 2 Si 5 N 8 :Eu. 
     
     
       4. The light emitting device as cited in  claim 1  wherein an average particle diameter of the second fluorescent material of the covering member is less than or equal to 10 μm. 
     
     
       5. The light emitting device as cited in  claim 1  wherein an amount of the second fluorescent material of the covering member is greater than or equal to 0.5 mass % and less than or equal to 10 mass % with respect to resin in the covering member. 
     
     
       6. The light emitting device as cited in  claim 1  wherein an amount of the light reflecting material of the covering member is greater than or equal to 10 mass % and less than or equal to 100 mass % with respect to resin in the covering member. 
     
     
       7. The light emitting device as cited in  claim 1  wherein a minimum thickness of the covering member measured perpendicular to a lateral surface of the light emitting element is less than or equal to 300 μm. 
     
     
       8. The light emitting device as cited in  claim 1  wherein the light reflecting material of the covering member comprises at least one compound selected from titanium dioxide, silicon dioxide, zirconium dioxide, and alumina. 
     
     
       9. The light emitting device as cited in  claim 1  wherein a change in chromaticity coordinates with angular direction from a direction perpendicular to a light emitting surface of the wavelength conversion member to a direction rotated by 80° is less than or equal to 0.003 in both x-axis and y-axis directions, where the x-axis and y-axis are mutually perpendicular and lie in the plane of the wavelength conversion member light emitting surface. 
     
     
       10. A light emitting device comprising:
 a light emitting element having a dominant wavelength in a range greater than or equal to 380 nm and less than or equal to 470 nm; 
 a wavelength conversion member that is disposed on the light emitting element and comprises a first fluorescent material; and 
 a covering member that covers sides of the wavelength conversion member and surrounds the light emitting element, 
 wherein the light emitting device has an emission spectrum having a dominant wavelength in a range greater than or equal to 610 nm and less than or equal to 780 nm, 
 wherein the covering member comprises light reflecting material and a second fluorescent material, 
 wherein a dominant wavelength of an emission spectrum of the second fluorescent material differs from the dominant wavelength of the emission spectrum of the light emitting device by less than or equal to 30 nm, 
 wherein the second fluorescent material of the covering member comprises at least one compound selected from (Ca, Sr)AlSiN 3 :Eu and (Ca, Sr, Ba) 2 Si 5 N 8 :Eu, and 
 wherein the first fluorescent material of the wavelength conversion member comprises at least one compound selected from (Ca, Sr)AlSiN 3 :Eu and (Ca, Sr, Ba) 2 Si 5 N 8 :Eu.